Code review comment for lp://staging/~makyo/juju-core/upgradecharm3-1171548

Reviewers: mp+167331_code.launchpad.net,

Message:
Please take a look.

Description:
Add UpgradeCharm to the API

This branch adds upgrade charm functionality to the API (branch 3/3 in
the process).

https://code.launchpad.net/~makyo/juju-core/upgradecharm3-1171548/+merge/167331

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/9975045/

Affected files:
   A [revision details]
   M state/api/client.go
   M state/api/params/params.go
   M state/apiserver/client.go
   M state/apiserver/perm_test.go
   A state/statecmd/upgradecharm.go
   A state/statecmd/upgradecharm_test.go